Abrasion and/or puncture resistant fabrics, airbag cushions, and methods

ABSTRACT

Typical road surfaces are concrete, and gravel filled asphalt. They are very abrasive to fabrics that slide on those surfaces. For the new side impact curtain-type airbag, in a rollover situation, the airbag needs to protect the occupant from directly contacting the road hazard and should not deflate quickly or break when sliding on such road surfaces. We have found that a layer of elastomer can provide much better abrasion resistance than a layer of heavy industrial fabric. A Jacquard bag coated with 1.2 oz/yd 2  polyurethane showed significant increase in air leakage rate after 5 cycles of concrete sliding abrasion. A 3 mil thick polyurethane film was laminated to the coated Jacquard woven airbag. After 110 cycles of sliding abrasion using the same concrete, no visual damage or change in bag leakage was observed. This finding indicates surprisingly better abrasion resistance of a thin elastomer film than a heavy industrial fabric.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S.provisional Patent Application Serial No. 60/229,112, filed on Aug. 30,2000, hereby incorporated by reference herein.

FIELD OF THE INVENTION

[0002] This invention relates generally to abrasion resistant and/orpuncture resistant fabrics, coated, layered and/or laminated inflatablefabrics, and methods. More particularly, it concerns airbag cushions towhich films, fabrics, layers, and/or coatings have been applied andwhich exhibit enhanced abrasion resistance and/or puncture resistance.The inventive inflatable fabrics are especially suited for use inautomotive restraint cushions that require abrasion resistance and/orpuncture resistance (such as side curtain airbags).

BACKGROUND OF THE INVENTION

[0003] Side curtain airbags differ from driver side and passenger sideairbags in that side curtain airbags preferably retain at least half oftheir inflated pressure for a period of 5 seconds or longer. Sidecurtain airbags must retain their fill for a longer period since arollover event would occur over some duration rather than, for example,an instantaneous front or rear impact.

[0004] Further, side curtain airbags which provide for rolloverprotection not only must keep their fill for a certain duration, butalso should provide some abrasion and/or puncture resistance so thatthey do not lose their inflation as the vehicle rolls and the exteriorof the bag contacts a broken window, asphalt, concrete, debris, and/orthe like.

[0005] Although it has been known to provide low permeability driver andpassenger side airbag fabrics and airbag cushions, attempts atconstructing side curtain airbags and in particular side curtain airbagswith rollover protection has been problematic.

[0006] Airbags for motor vehicles are known and have been used for asubstantial period of time. A typical construction material for airbagshas been a polyester or nylon fabric, coated with an elastomer such asneoprene, or silicone. The fabric used in such bags is typically a wovenfabric formed from synthetic yarn by weaving practices that are wellknown in the art.

[0007] The coated material has found acceptance because it acts as animpermeable barrier to the inflation medium. This inflation medium isgenerally a nitrogen, argon, or similar gas or gas blend generated froma gas generator or inflator. Such gas is conveyed into the cushion at arelatively warm temperature. The coating obstructs the permeation of thefabric by such hot gas, thereby permitting the cushion to rapidlyinflate without undue decompression during a collision event.

[0008] Airbags may also be formed from uncoated fabric which has beenwoven in a manner that creates a product possessing low permeability orfrom fabric that has undergone treatment such as calendering to reducepermeability. Fabrics which reduce air permeability by calendering orother mechanical treatments after weaving are disclosed in U.S. Pat. No.4,921,735; U.S. Pat. No. 4,977,016; and U.S. Pat. No. 5,073,418 (allincorporated herein by reference).

[0009] Silicone coatings typically utilize either solvent based orcomplex two component reaction systems. Dry coating weights for siliconehave been in the range of about 3 to 4 ounces per square yard or greaterfor both the front and back panels of side curtain airbags. As will beappreciated by one of ordinary skill in this art, high add on weightssubstantially increase the cost of the base fabric for the airbag andmake packing within small airbag modules very difficult. Furthermore,silicone exhibits very low tensile strength and elongation at breakcharacteristics which do not withstand high pressure inflation easilywithout the utilization of very thick coatings.

[0010] The use of certain polyurethanes as coatings as disclosed in U.S.Pat. No. 5,110,666 to Menzel et al. (herein incorporated by reference)permits low add on weights reported to be in the range of 0.1 to 1ounces per square yard but the material itself is relatively expensiveand is believed to require relatively complex compounding andapplication procedures due to the nature of the coating materials. The5,110,666 patent, however, fails to disclose any pertinent elasticityand/or tensile strength characteristics of their particular polyurethanecoating materials. Furthermore, there is no discussion pertaining to theimportance of the coating ability (and thus correlated low airpermeability) at low add-on weights of such polyurethane materials onside curtain airbags (only for fabrics which are utilized within driveror passenger side cushions).

[0011] All airbags must be inflatable extremely quickly; upon sensing acollision, in fact, airbags usually reach peak pressures within 10 to 20milliseconds. Regular driver side and passenger side air bags aredesigned to withstand this enormous inflation pressure; however, theyalso deflate very quickly in order to effectively absorb the energy fromthe vehicle occupant hitting the bag. Such driver and passenger sidecushions (airbags) are thus made from low permeability fabric, but theyalso deflate quickly at connecting seams (which are not coated toprevent air leakage) or through vent holes. Furthermore, the low add-oncoatings taught within Menzel, and within U.S. Pat. No. 5,945,186 to Liet al., would not provide long-term gas retention; they would actuallynot withstand the prolonged and continuous pressures supplied byactivated inflators for more than about 2 seconds, at the most. The lowpermeability of these airbag fabrics thus aid in providing a smalldegree of sustained gas retention within driver and passenger airbagcushions to provide the deflating cushioning effects necessary forsufficient collision protection. Such airbag fabrics would not functionwell with side curtain airbags, since, at the very least, the connectingseams which create the pillowed, cushioned structures within suchairbags, as discussed in greater detail below, would not be coated. Asthese areas provide the greatest degree of leakage during and afterinflation, the aforementioned patented low coating low permeabilityairbag fabrics would not be properly utilized within side curtainairbags.

[0012] As alluded to above, there are three primary types of differentairbags, each for different end uses. For example, driver-side airbagsare generally mounted within steering columns and exhibit relativelyhigh air permeabilities in order to act more as a cushion for the driverupon impact. Passenger-side airbags also comprise relatively high airpermeability fabrics which permit release of gas either therethrough orthrough vents integrated therein. Both of these types of airbags aredesigned to protect persons in sudden collisions and generally burst outof packing modules from either a steering column or dashboard (and thushave multiple “sides”).

[0013] Side curtain airbags, however, have been designed primarily toprotect passengers during rollover crashes by retaining their inflationstate for a long duration and generally unroll from packing containersstored within the roofline along the side windows of an automobile (andthus have a back and front side only). Side curtain airbags thereforenot only provide cushioning effects but also should provide protectionfrom broken glass and other debris. As such, it is imperative that sidecurtain airbags, as noted above, retain large amounts of gas, as well ashigh gas pressures, to remain inflated throughout the longer timeperiods of the entire potential rollover situation.

[0014] To accomplish this, these side curtains are generally coated withvery large amounts of sealing materials on both the front and backsides. Since most side curtain airbag fabrics comprise woven blanks thatare either sewn, sealed, or integrally woven together, discrete areas ofpotentially high leakage of gas are prevalent, particularly at andaround the seams. It has been accepted as a requirement that heavycoatings were necessary to provide the low permeability (and thus highleak-down time) necessary for side curtain airbags. Without such heavycoatings, such airbags would most likely deflate too quickly and thuswould not function properly during a rollover collision. As will be wellunderstood by one of ordinary skill in this art, such heavy coatings addgreat cost to the overall manufacture of the target side curtainairbags. There is thus a great need to manufacture low permeability sidecurtain airbags with less expensive (preferably lower coating add-onweight) coatings without losing the aging, humidity, and permeabilitycharacteristics necessary for proper functioning upon deployment.

[0015] Furthermore, there is a current drive to store such lowpermeability side curtain airbags within cylindrically shaped modules.Since these airbags are generally stored within the rooflines ofautomobiles, and the area available is quite limited, there is always agreat need to restrict the packing volume of such restraint cushions totheir absolute minimum. However, the previously practiced lowpermeability side curtain airbags have proven to be very cumbersome tostore in such cylindrically shaped containers at the target automobile'sroofline. The actual time and energy required to roll such heavilycoated low permeability articles as well as the packing volume itself,has been very difficult to reduce. Furthermore, with such heavy coatingsutilized, the problems of blocking (i.e., adhering together of thedifferent coated portions of the cushion) are amplified when sucharticles are so closely packed together. The chances of delayedunrolling during inflation are raised when the potential for blocking ispresent. Thus, a very closely packed, low packing volume, low blocking,low permeability side curtain airbag is highly desirable.

SUMMARY OF THE INVENTION

[0016] In light of the background above, it is an object of the presentinvention to provide an abrasion resistant and/or puncture resistantfabric, airbag cushion, and/or method.

[0017] In accordance with a more particular object of the presentinvention, there is provided an improved side curtain airbag whichaffords rollover protection.

[0018] It is still another object to provide an airbag fabric or cushionwhich has both abrasion and puncture resistance.

[0019] It is yet still another object of the present invention toprovide an airbag which has an inner or inside surface, wall,construction, or coating adjacent the occupant which is at least one oflighter, softer, more flexible, less abrasive, and the like than anouter or outside surface, wall, construction, or coating adjacent thewindow of a vehicle.

[0020] It is still another object of the present invention to provide anairbag having differing inner and outer surfaces, constructions, walls,coatings, or the like, with the outer surface, wall, construction,coating, or the like having better puncture resistance and/or abrasionresistance than the inner surface, wall, construction, coating, or thelike.

[0021] Also, it can be readily seen that there exists a need for a lowpermeability, side curtain airbag that provides a necessarily highleak-down time upon inflation and after long-term storage.

[0022] It is therefore an object of this invention to provide a coatedand/or laminated airbag possessing extremely high leak-down timecharacteristics after inflation and thus complementary low permeabilitycharacteristics. Another object of the invention is to provide aninexpensive side curtain airbag cushion. A further object of thisinvention is to provide a highly effective airbag coating or adhesiveformulation or laminate construction providing extremely lowpermeability airbag structures after inflation. An additional object ofthis invention is to provide an airbag which not only providesbeneficial and long-term low permeability, but also exhibits excellentlong-term storage stability (through heat aging and humidity agingtesting). Yet another object of the invention is to provide a lowpermeability side curtain airbag possessing a low rolled packing volumeand non-blocking characteristics for effective long-term storage withinthe roofline of an automobile.

[0023] Accordingly, one embodiment this invention is directed to anairbag cushion comprising a coated fabric, wherein said fabric islaminated with a film, wherein said film is of about 0.5-10.0 milsthick, preferably 2-4 mils, and/or wherein said airbag cushion, afterlong-term storage, exhibits a characteristic leak-down time of at least5 seconds. Also, this invention concerns an airbag cushion comprising acoated fabric, wherein said fabric is coated with a laminate film;wherein said laminate film possesses a tensile strength of at least2,000 psi and an elongation of at least 180%; and wherein said airbagcushion, after long-term storage, exhibits a characteristic leak-downtime of at least 5 seconds.

[0024] A mil is a unit of thickness equal to one thousandth of an inch(0.0254 millimeter). A mil of coating is approximately equal to aboutone ounce per square yard of coating.

[0025] The term “characteristic leak-down time” is intended to encompassthe measurement of time required for the entire amount of inflation gasintroduced within an already-inflated (to a peak initial pressure which“opens” up the areas of weak sealing) and deflated airbag cushion toleak out upon subsequent re-inflation at a constant pressure of 10 psi.It is well known and well understood within the airbag art, andparticularly concerning side curtain (low permeability) airbag cushions,that retention of inflation gas for long periods of time is of utmostimportance during a collision. Side curtain airbags are designed toinflate as quickly as driver- and passenger-side bags, but they mustdeflate very slowly to protect the occupants during roll over and sideimpact. Thus, it is imperative that the bag exhibit a very low leakagerate after the bag experiences peak pressure during the instantaneous,quick inflation. Hence, the coating on the bag must be strong enough towithstand the shock and stresses when the bag is inflated so quickly.Thus, a high characteristic leak-down time measurement is paramount inorder to retain the maximum amount of beneficial cushioning gas withinthe inflated airbag. Airbag leakage after inflation (and after peakpressure is reached) is therefore closely related to actual pressureretention characteristics. The pressure retention characteristics(hereinafter referred to as “leak-down time”) of already-inflated anddeflated side curtain airbags can be described by a characteristicleak-down time t, wherein:${t({second})} = {\frac{{Bag}\quad {volume}\quad \left( {ft}^{3} \right)}{{{Volumetric}\quad {leakage}\quad {rate}\quad \left( {SCFH}^{*} \right)\quad {at}\quad 1} - {psi}} \times 3600}$ ^(*)SCFH : standard  cubic  feet  per  hour.

[0026] It is understood that the 10 psi constant is not a limitation tothe invention; but merely the constant pressure at which thecharacteristic leak-down time measurements are made. Thus, even if thepressure is above or below this amount during actual inflation or afterinitial pressurizing of the airbag, the only limitation is that if oneof ordinary skill in the art were to measure the bag volume and dividethat by the volumetric leakage rate time (measured by the amount leakingout of the target airbag during steady state inflation at 10 psi), theresultant measurement in time would be at least 5 seconds. Preferably,this time is greater than about 9 seconds; more preferably, greater thanabout 15 seconds; and most preferably, greater than about 20 seconds.

[0027] Alternatively, and in a manner of measurement with uninflatedside curtain airbags, the term “leak-down time” may be measured as theamount of time required for at least half of the introduced inflationgas to escape from the target airbag after initial peak pressure isreached. Thus, this measurement begins the instant after peak initialpressure is reached upon inflation (such as, traditionally, about 30psi) with a standard inflation module which continues to pump gas intothe target airbag during and after peak initial pressure is reached. Itis well understood that the pressure of gas forced into the airbag afterpeak initial pressure is reached will not remain stable (it decreasesduring the subsequent introduction of inflation gas), and that thetarget airbag will inevitably permit escape of a certain amount ofinflation gas during that time. The primary focus of such side curtainairbags (as noted above) is to remain inflated for as long as possiblein order to provide sufficient cushioning protection to vehicleoccupants during rollover accidents. The greater amount of gas retained,the better cushioning effects are provided the passengers. Thus, thelonger the airbag retains a large amount of inflation gas, andconsequently the greater the characteristic leak-down time, the bettercushioning results are achieved. At the very least, the inventive airbagshould retain at least half of its inflated gas volume 5 secondssubsequent to reaching peak initial pressure. Preferably, this time is 9seconds, more preferably 15 seconds, and most preferably 20 seconds ormore.

[0028] Likewise, the term, “after long-term storage” encompasses eitherthe actual storage of an inventive airbag cushion within an inflatorassembly (module) within an automobile, and/or in a storage facilityawaiting installation. Such a measurement is generally accepted, and iswell understood and appreciated by the ordinarily skilled artisan, to bemade through comparable analysis after representative heat and humidityaging tests. These tests generally involve 107° C. oven aging for 16days, followed by 83° C. and 95% relative humidity aging for 16 days andare universally accepted as proper estimations of the conditions oflong-term storage for airbag cushions. Thus, this term encompasses suchmeasurement tests. The inventive airbag fabrics should exhibit propercharacteristic leak-down times after undergoing such rigorouspseudo-storage testing.

[0029] Typical road surfaces are concrete, and gravel filled asphalt.They are very abrasive to fabrics that slide on those surfaces. For thenew side impact curtain-type airbag (side curtain airbag), in a rolloversituation, the airbag needs to protect the occupant from directlycontacting the road hazard and should not deflate quickly or break whensliding on such road surfaces.

[0030] We have found that fabric usually provides excellent abrasionresistance in most cases, and that fabrics laminated to or coated with atough rubber material provide abrasion resistance. In the case ofabrasion over typical road surfaces, we have surprisingly found that alayer of elastomer can provide much better abrasion resistance than alayer of heavy industrial fabric.

[0031] We have tested Jacquard woven airbags coated and laminated withdifferent materials. The airbag is first inflated to and maintained at10 psi air pressure, then a 13 lb., 1.5 ft. long concrete block was laidon one area of the bag and allowed to slide back and forth. A Jacquardbag coated with 1.2 oz/yd² polyurethane showed significant increase inair leakage rate after 5 cycles of concrete sliding abrasion. To see ifan extra layer of heavy fabric would protect the airbag from suchabrasion, a 420 denier, 49×49 plain weave airbag fabric was laminated ona coated Jacquard woven bag. The 420 denier fabric had many brokenfilaments in a few cycles. In about 25 cycles, the yarns perpendicularto the concrete sliding direction were all broken and removed by thesliding abrasion. After 25 cycles, the remaining laminated 420 denierfabric provided very little protection for the Jacquard woven bagagainst the sliding abrasion. A 3 mil thick Duraflex PT 9400polyurethane film was laminated to a coated Jacquard woven airbag. After110 cycles of sliding abrasion using the same concrete, no visual damageor change in bag leakage was observed. This finding indicatessurprisingly better abrasion resistance of a thin elastomer film than aheavy industrial fabric.

[0032] We have studied airbags laminated with different films and filmswith different thicknesses. We have noted that the toughness of theelastomer needs to be above a certain value in order to provide thenecessary abrasion resistance.

[0033] One layer of fabric may be used on top of this elastomeric layerfor puncture resistance. Preferred elastomeric materials arepolyurethane, Neoprene and other rubbers with high toughness. Thecombination of an elastomeric layer and a layer of extra fabric canprovide both abrasion and puncture resistance. The elastomer layer canact as an abrasion resistant layer, gas barrier and adhesive layerbetween the base airbag fabric and the extra fabric top layer.

[0034] At least one embodiment of the present invention provides airbagswith excellent abrasion resistance against typical road surfaces byhaving a tough elastomeric layer with a thickness greater than about 0.5mil, preferably about 1.5 mil or more. Compared to a similar structurelaminated with a layer of heavy fabric, the inventive structure hasbetter abrasion resistance, better flexibility, is thinner, and costsless.

[0035] This layer of elastomer can be applied by film lamination,transfer coating, extrusion coating, and other coating methods. Thislayer of elastomer does not have to have uniform thickness. Instead ofan elastomer layer, one can print elastomer dots on the fabric withsmall spacing between the dots.

[0036] Traditionally, driver and passenger airbags are energy absorbingsafety barriers between an occupant and the interior of a vehicle, suchas dashboard, windshield and steering wheel. New side impact curtainairbags (side curtain airbags) are now providing a safety barrierbetween an occupant and exterior hazards in an auto-accident. Due to thepossible presence of various sharp objects such as broken window glass,nails, and jagged sheet metal in a collision, side curtain airbags withpuncture resistance are needed but not currently provided to the market.The current driver side airbag or passenger airbag construction does notprovide good puncture resistance at its working inflated state tohazards such as broken window glass.

[0037] The present invention encompasses the following constructionsthat provide superior resistance to puncture:

[0038] 1. Triple layer sandwich—On at least the side facing the exteriorof a vehicle, the airbag has a fabric/elastomer/fabric three layerstructure (FIG. 12C). The outer fabric layer provides some abrasionresistance and combines with the strength of the inner fabric layer toprovide puncture resistance. The middle elastomeric layer providesabrasion resistance and the low gas permeability to allow the airbag tostay inflated for a desired length of time at a desired pressure. Theelastomeric layer can also function as an adhesive layer to bond theouter and inner fabric layers together. The choice of fabricconstructions is crucial in obtaining the desired puncture resistance.To obtain the desired puncture resistance, it is preferred that thefabric be constructed from high strength yarn such as high tenacityNylon, polyester, polyethylene (such Spectra™), and aramids (such asKevlar™). The fabric should have high yarn density to prevent sharpobjects from going through the yarn interstices. It is also desirablefor the sandwich to be thin so that the whole airbag can be packed intoa small volume. Therefore, fabrics from small denier yarn at high pickand end counts are preferred.

[0039] 2. Airbag with an elastomeric inner bladder that is looselyattached to the outer fabric layer. The inner bladder has the ability tostretch substantially without breaking or bursting when a sharp objectpenetrates through the outer layer of airbag fabric. Thus, the innerbladder functions much like a puncture resistant inner tube for avehicle tire (FIG. 12K).

[0040] 3. A puncture resistant barrier interposed between the airbag andexterior of the vehicle when the airbag is deployed. The barrier may ormay not be attached firmly to the airbag itself (FIG. 12L).

[0041] 4. A system of small gas filled cells interposed between theairbag and exterior of vehicle when the airbag is deployed. The systemof cells is designed to support the airbag and keep sharp objects frompenetrating the airbag even when some of the cells themselves arepunctured (FIG. 12M).

[0042] To prevent puncture and premature deflation of an airbag during acollision, various combinations of fabric, coating and films are used inaccordance with selected embodiments of the present invention to achievethe desired result.

[0043] It is common practice to coat a fabric or woven structure withthe same coating and the same weight coating on both sides. The natureof at least -one embodiment of the present invention is to provide aproduct that has a coating on both sides of the fabric or wovenstructure that can provide different characteristics or performance foreach side (side 102, 104 of airbag 126 of FIGS. 3 and 6). The method ofaccomplishing this can be through utilizing a different weight coatingon one side versus another or using a different chemical on each side.The coating can be tailored to the performance that is required e.g. theoutside (104) OPW can be coated with a tough polymer to resist punctureor abrasion while the side toward the occupant (102) can be coated witha non abrasive coating. The primary use of this would be for jacquardwoven inflatable restraints, but could be used for any inflatablefabric, cushion, airbag, etc.

[0044] Selected objects of at least one embodiment of the presentinvention include:

[0045] On a jacquard woven fabric provide a different weight coating oneach side based on end use performance requirements.

[0046] On a jacquard woven fabric provide a different coating on eitherside based on end use performance requirements.

[0047] On a flat fabric provide a different weight coating on eitherside.

[0048] Allows the design of coated fabrics tailored to specific end useperformance requirements.

[0049] A sewn bag made of coated fabric with different coatings on eachside.

[0050] Curtain airbags used for rollover protection are typicallydesigned as one gas holding system. In rollover accidents, these airbagshave a high probability of coming in contact with road and broken glassdebris. Any puncture or abrasion to the fabric structure of the bag awayfrom the occupant side because of the debris from the broken glass orfrom the road can make this entire system ineffective. Also, the portionof the curtain bag closer to the occupant should be less abrasive to theoccupant during deployment or the pressurization phase.

[0051] In order to accomplish this, quite different properties are givento either side of the side curtain. For example, different size yarnscan be used on each side of the curtain, yarns of bigger diameter andhigher tenacity can be used on the side away from the occupant, and thelike. Bigger yarns provide higher surface area and hence provide betterresistance to puncture. On the side of the side curtain where theoccupant comes in contact, finer yarns can be used in order to begentler on the occupant.

[0052] Curtain bags produced with many different technologies like sewn,jacquard or dobby woven, welded or sealed seams can use this approach.

[0053] Additional objects and advantages of the invention will be setforth in part in the description which follows, and in part will beobvious from the description, or may be learned by practice for theinvention. It is to be understood that both the foregoing generaldescription and the following detailed description of preferredembodiments are exemplary and explanatory only, and are not to be viewedas in any way restricting the scope of the invention as set forth in theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054]FIG. 1 depicts the side, inside view of a vehicle prior todeployment of the inventive side curtain airbag.

[0055]FIG. 2 depicts the side, inside view of the vehicle afterdeployment of the inventive side curtain airbag.

[0056]FIG. 3 depicts an inside side view of the side curtain airbag.

[0057]FIG. 4 provides a side view of a side curtain airbag container.

[0058]FIG. 5A provides a schematic cross-sectional view of a storedairbag within the container of FIG. 4.

[0059]FIG. 5B provides a schematic cross-sectional view of analternatively stored airbag.

[0060]FIG. 6 depicts an outside side view of the airbag of FIG. 3.

[0061]FIG. 7 is a graphical representation of resistance to abrasion bygravel.

[0062]FIG. 8 is a graphical illustration of resistance to abrasion byconcrete.

[0063]FIG. 9 is a graphical representation of resistance to puncture byglass (time to lose half of initial pressure).

[0064]FIG. 10 is a cross-sectional view of an inventive all-woveninflatable fabric showing double and single layer areas including twoseparate single layer areas.

[0065]FIG. 11 is a weave diagram illustrating a potentially preferredrepeating pick pattern formed using repeating plain weave and basketweave four-pick arrangements.

[0066] FIGS. 12A-12M are schematic cross-sectional layer diagrams ofselected embodiments of the side wall of the airbag toward the window.

DETAILED DESCRIPTION OF THE INVENTION

[0067] In accordance with at least one embodiment, the inventive coatingand/or film preferably possess a tensile strength of at least 2,000 psiand an elongation to break of greater than about 180%. Preferably, thetensile strength is at least 3,000 psi, more preferably, 6,000 psi, andmost preferably at least about 8,000 psi (the high end is basically thehighest one can produce which can still adhere to a fabric surface). Thepreferred elongation to break is more than about 200%, more preferablymore than about 300%, and most preferably more than about 600%. Thesecharacteristics of the film and/or coating translate to a material thatis both very strong (and thus will withstand enormous pressures both atinflation and during the time after inflation and will not easily break)and can stretch to compensate for such large inflation, etc., pressures.The film itself is produced prior to actual contact with the targetairbag cushion, or fabric, surface. In order to apply such a film, alamination procedure is performed through the simultaneous exposure ofheat and pressure over the film while in contact with the targetsurface. The laminate may be applied over any portion of the targetstructure, although preferably it coats the entire exterior surface ofthe cushion or fabric. Also, more than one laminated film may be presenton the target cushion as one type of film (possessing certain tensilestrength and elongation characteristics) may be preferably applied tocertain discrete areas of the target cushion while a different film withdifferent characteristics may be selected at other locations (such as atthe seams). The only requirement is that the final product exhibit theaforementioned high leak-down properties. The film and/or coatingappears to act by “cementing” the contacted individual yarns in placeand possibly preventing leakage through open areas between woven yarnsand/or stitches. During inflation, then, the film and/or coatingprevents leakage through the interstitial spaces between the yarns andaids in preventing yarn shifting (which may create larger spaces forpossible gas escape).

[0068] The utilization of such high tensile strength and high elongationat break components permits the consequent utilization, surprisingly, oflow add-on weight amounts of such films or coatings. Normally, therequired coatings (which are not films, but actual coating formulationsapplied to the surface which then may form non-laminated films) on sidecurtain airbags are at least 3.5 ounces per square yard (with thestandard actually higher than that, at about 4.0). The inventive airbagcushions require merely about 0.5 or more mils thick or about 0.5 ouncesper square yard of the desired film and/or coating to effectuate thedesired high characteristic leak-down time (low permeability).Furthermore, the past coatings were required to exhibit excellent heatand humidity aging stability. Unexpectedly, even at such low add-onamounts, and particularly with historically questionable coatingmaterials (polyurethanes, for example), the inventive coatings, andconsequently, the inventive coated airbag cushions, exhibit excellentheat aging and humidity aging characteristics. Thus, the coatingcompositions and coated airbags are clearly improvements within thisspecific airbag art.

[0069] Of particular interest as the desired films are polyurethanes,although any film which possesses the same desired tensile strength andelongation characteristics noted above may function within thisinventive low permeability airbag cushion. Copolymers of polyurethanes,polyamides, and the like, may be utilized, as merely one type ofexample. Also, such films may or may not be cross-linked on the airbagsurface. Preferably, the film is a polyurethane and most preferably is apolycarbonate polyurethane or a polyurethane film based onpolytetramethylene glycol diol (available from Deerfield Urethane, Inc.,Ivyland, Pa., under the tradename Dureflex™ PT9400). This specific filmexhibits a tensile strength of 8,000 psi and an elongation at break ofabout 600%. Such a film may be added in an amount of as low as about 0.5mils or ounces per square yard on the desired cushion and still providethe requisite high characteristic leak-down time. Of course, any otherfilm meeting the characteristics as noted above is encompassed withinthis invention; however, the add-on weights of other available films maybe greater than this preferred one, depending on the actual tensilestrength and elongation properties available. However, an upper limit ofabout 10.0 mils or ounces per square yard should not be exceeded to meetthis invention. The desired films may be added in multiple layers ifdesired as long the required thickness for the overall coating is notexceeded. Alternatively, the multiple layer film/coating system may alsobe utilized as long as at least one film possessing the desired tensilestrength and elongation at break is utilized and the requisite lowpermeability is exhibited.

[0070] Other possible components present within or on these films arethickeners, antioxidants, flame retardants, coalescent agents, adhesionpromoters, and colorants. In accordance with the potentially preferredpractices of the present invention, a primer or adhesive coating isfirst applied to the target cushion surface. Upon drying of this firstlayer, the desired film is then laminated through heat and pressure tothe selected areas of the target surface for a sufficient time toeffectuate lamination. Preferably, the preferred film (or films) willnot include any silicone, due to the extremely low tensile strength(typically below about 1,500 psi) characteristics exhibited by suchmaterials. However, in order to provide effective aging and non-blockingbenefits, such components may be applied to the film as a topcoat aslong as the add-on weight of the entire film and topcoat does not exceedabout 10.0 ounces per square yard. Additionally, elastomers comprisingpolyester or polyether segments or other similar components, areundesirable, particularly at very low add-on weights (i.e., 0.8-1.2oz/yd²) due to stability problems in heat and humidity aging (polyesterseasily hydrolyze in humidity and polyethers easily oxidize in heat);however, such elastomers may be utilized in topcoat formulations aslong, again, as the 10.0 ounces per square yard is not exceeded. Forpuncture resistance, silicone can be used but should be added in greaterquantities than other elastomers.

[0071] Among the other additives particularly preferred within or on thefilm (or films) are heat stabilizers, flame retardants, primeradhesives, and materials for protective topcoats. A potentiallypreferred thickener is marketed under the trade designation NATROSOL®250 HHXR by the Aqualon division of Hercules Corporation which isbelieved to have a place of business at Wilmington, Del. In order tomeet Federal Motor Vehicle Safety Standard 302 flame retardantrequirements for the automotive industry, a flame retardant is alsopreferably added to the compounded mix. One potentially preferred flameretardant is AMSPERSE F/R 51 marketed by Amspec Chemical Corporationwhich is believed to have a place of business at Gloucester City, N.J.As noted above, primer adhesives may be utilized to facilitate adhesionbetween the surface of the target fabric and the film itself. Thus,although it is preferable for the film to be the sole component of theentire coating in contact with the fabric surface, it is possible toutilize adhesion promoters, such as isocyanates, epoxies, functionalsilanes, and other such resins with adhesive properties, withoutdeleteriously effecting the ability of the film to provide the desiredlow permeability for the target airbag cushion. A topcoat component, aswith potential silicones, as noted above, may also be utilized toeffectuate proper non-blocking characteristics to the target airbagcushion. Such a topcoat may perform various functions, including, butnot limited to, improving aging of the film (such as with silicone) orproviding blocking resistance due to the adhesive nature of the coatingmaterials (most noticeably with the preferred polyurethanepolycarbonates).

[0072] Airbag fabrics must pass certain tests in order to be utilizedwithin restraint systems. One such test is called a blocking test whichindicates the force required to separate two portions of coated fabricfrom one another after prolonged storage in contact with each other(such as an airbag is stored). Laboratory analysis for blocking entailspressing together coated sides of two 2 inch by 2 inch swatches ofairbag fabric at 5 psi at 100° C. for 7 days. If the force required topull the two swatches apart after this time is greater than 50 grams, orthe time required to separate the fabrics utilizing a 50 gram weightsuspended from the bottom fabric layer is greater than 10 seconds, thecoating fails the blocking test. Clearly, the lower the requiredseparating force, the more favorable the coating. For improved blockingresistance (and thus the reduced chance of improper adhesion between thepacked fabric portions), topcoat components may be utilized, such astalc, silica, silicate clays, and starch powders, as long as the add-onweight of the entire elastomer composition (including the topcoat) doesnot exceed about 10.0 ounces per square yard (and preferably exists at amuch lower level, about 1.5, for instance).

[0073] Two other tests which the specific coated airbag cushion mustpass are the oven (heat) aging and humidity aging tests. Such tests alsosimulate the storage of an airbag fabric over a long period of time uponexposure at high temperatures and at relatively high humidities. Thesetests are actually used to analyze alterations of various differentfabric properties after such a prolonged storage in a hot ventilatedoven (>100° C.) (with or without humid conditions) for 2 or more weeks.For the purposes of this invention, this test was used basically toanalyze the air permeability of the coated side curtain airbag bymeasuring the characteristic leak-down time (as discussed above, indetail). The initially produced and stored inventive airbag cushionshould exhibit a characteristic leak-down time of greater than about 5seconds (upon re-inflation at 10 psi gas pressure after the bag hadpreviously been inflated to a peak pressure above about 15 psi andallowed to fully deflate) under such harsh storage conditions. Sincepolyurethanes, the preferred elastomers in this invention, may bedeleteriously affected by high heat and humidity (though not asdeleteriously as certain polyester and polyether-containing elastomers),it may be prudent to add certain components within a topcoat layerand/or within the elastomer itself. Antioxidants, antidegradants, andmetal deactivators may be utilized for this purpose. Examples include,and are not intended to be limited to, Irganox® 1010 and Irganox® 565,both available from CIBA Specialty Chemicals. This topcoat may alsoprovide additional protection against aging and thus may include topcoataging improvement materials, such as, and not limited to, polyamides,NBR rubbers, EPDM rubbers, and the like, as long as the elastomercomposition (including the topcoat) does not exceed the about 10.0ounces per square yard (preferably much less than that, about 2-4) ofthe add-on weight to the target fabric.

[0074] The substrate to which the thin film coatings are applied to formthe airbag base fabric in accordance with at least one embodiment of thepresent invention is preferably a woven fabric formed from yarnscomprising synthetic fibers, such as polyamides or polyesters. Such yarnpreferably has a linear density of about 105 denier to about 840 denier,more preferably from about 210 to about 630 denier. Such yarns arepreferably formed from multiple filaments wherein the filaments havelinear densities of about 7 denier per filaments or less, morepreferably about 6 dpf or less, and most preferably about 4 dpf or less.In the more preferred embodiment such substrate fabric will be formedfrom fibers of nylon, and most preferred is nylon 6,6. It has been foundthat such polyamide materials exhibit particularly good adhesion andmaintenance of resistance to hydrolysis when used in combination withthe coating according to the present invention. Such substrate fabricsare preferably woven using fluid jet weaving machines as disclosed inU.S. Pat. Nos. 5,503,197 and 5,421,378 to Bower et al. (incorporatedherein by reference). Such woven fabric will be hereinafter referred toas an airbag base fabric. As noted above, when the inventive airbag is aside curtain airbag, it must exhibit extremely low permeability. Asnoted previously and extensively, such side curtain airbags (a.k.a.,cushions) must retain a large amount of inflation gas during a collisionin order to accord proper long-duration cushioning protection topassengers during rollover accidents. Any standard side curtain airbagmay be utilized in combination with the inventive coatings, films,fabrics, layers, and/or the like to provide a product which exhibits thedesired characteristic leak-down times as noted above. Most side curtainairbags are produced through labor-intensive sewing or stitching (orother manner) together two separate woven fabric blanks to form aninflatable structure. Furthermore, as is well understood by theordinarily skilled artisan, such sewing, etc., is performed in strategiclocations to form seams (connection points between fabric layers) whichin turn produce discrete open areas into which inflation gasses may flowduring inflation. Such open areas thus produce pillowed structureswithin the final inflated airbag cushion to provide more surface areaduring a collision, as well as provide strength to the bag itself inorder to withstand the very high initial inflation pressures (and thusnot explode during such an inflation event).

[0075] Other side curtain airbag cushions exist which are of theone-piece woven variety. Basically, some inflatable airbags are producedthrough the simultaneous weaving of two separate layers of fabric whichare joined together at certain strategic locations (again, to form thedesired pillowed structures). Such cushions thus present seams ofconnection between the two layers. It is the presence of so many seams(in both multiple-piece and one-piece woven bags) which create theaforementioned problems of gas loss during and after inflation. Thepossibility of yarn shifting, particularly where the yarns shift in andat many different ways and amounts, thus creates the quick deflation ofthe bag through quick escaping of inflation gasses. Thus, the baseairbag fabrics do not provide much help in reducing permeability (andcorrelated characteristic leak-down times, particularly at relativelyhigh pressures). It is this seam problem which has primarily created theneed for the utilization of very thick, and thus expensive, coatings toprovide necessarily low permeability in the past.

[0076] Recently, a move has been made away from both the multiple-pieceside curtain airbags (which require great amounts of labor-intensivesewing to attached woven fabric blanks) and the traditionally producedone-piece woven cushions, to more specific one-piece woven fabrics whichexhibit substantially reduced floats between woven yarns tosubstantially reduce the unbalanced shifting of yarns upon inflation,such as described in U.S. Pat. No. 6,220,309, hereby completelyincorporated by reference herein. These one-piece woven bags aregenerally produced on dobby or jacquard fluid-jet looms, preferably theutilized one-piece airbag is made from a jacquard weaving process. Withsuch an improvement, the possibility of high leakage at seams issubstantially reduced. These airbags provide balanced weaveconstructions at and around attachment points between two layers offabrics such that the ability of the yarns to become displaced uponinflation at high pressures is reduced as compared with the standardone-piece woven airbags. Such inventive one-piece woven bags may stillbe problematic in that the weave intersections may be displaced uponhigh pressure inflation such that leakage may occur at too high a ratefor proper functioning. As a result, there is usually still a need tocoat such one-piece woven structures with materials which reduce and/oreliminate such an effect. However, such one-piece woven structurespermit extremely low add-on amounts of elastomeric coatings for lowpermeability effects. In fact, these inventive airbags functionextremely well with low add-on coatings below about 1.5 and as low asabout 0.8 ounces per square yard.

[0077] As described in U.S. Pat. No. 6,220,309, inflatable protectivecushions used in passenger vehicles are a component of relativelycomplex passive restraint systems. The main elements of these systemsare: an impact sensing system, an ignition system, a propellantmaterial, an attachment device, a system enclosure, and an inflatableprotective cushion. Upon sensing an impact, the propellant is ignitedcausing an explosive release of gases filing the cushion to a deployedstate which can absorb the impact of the forward movement of a body anddissipate its energy by means of rapid venting of the gas. The entiresequence of events usually occurs within about 100 milliseconds. In theundeployed state, the cushion is stored in or near the steering column,the dashboard, in a door, or in the back of a front seat placing thecushion in close proximity to the person or object it is to protect.

[0078] Inflatable cushion systems commonly referred to as air bagsystems have been used in the past to protect both the operator of thevehicle and passengers. Systems for the protection of the vehicleoperator have typically been mounted in the steering column of thevehicle and have utilized cushion constructions directly deployabletowards the driver. These driver-side cushions are typically of arelatively simple configuration in that they function over a fairlysmall well-defined area between the driver and the steering column. Onesuch configuration is disclosed in U.S. Pat. No. 5,533,755 to Nelsen etal., issued Jul. 9, 1996, the teachings of which are incorporated hereinby reference.

[0079] Inflatable cushions for use in the protection of passengersagainst frontal or side impacts must generally have a more complexconfiguration since the position of a vehicle passenger may not be welldefined and greater distance may exist between the passenger and thesurface of the vehicle against which that passenger might be thrown inthe event of a collision. Prior cushions for use in such environmentsare disclosed in U.S. Pat. No. 5,520,416 to Bishop; U.S. Pat. No.5,454,594 to Krickl; U.S. Pat. No. 5,423,273 to Hawthorn et al.; U.S.Pat. No. 5,316,337 to Yamaji, et al.; U.S. Pat. No. 5,310,216 to Wehneret al.; U.S. Pat. No. 5,090,729 to Watanabe; U.S. Pat. No. 5,087,071 toWallner et al.; U.S. Pat. No. 4,944,529 to Backhaus; and U.S. Pat. No.3,792,873 to Buchner et al.

[0080] The majority of commercially used restraint cushions are formedof woven fabric materials utilizing multifilament synthetic yarns ofmaterials such as polyester, nylon 6 or nylon 6,6 polymers.Representative fabrics for such use are disclosed in U.S. Pat. No.4,921,735 to Bloch; U.S. Pat. No. 5,093,163 to Krummheuer et al.; U.S.Pat. No. 5,110,666 to Menzel et al.; U.S. Pat. No. 5,236,775 to Swobodaet al.; U.S. Pat. No. 5,277,230 to Sollars, Jr.; U.S. Pat. No. 5,356,680to Krummheuer et al.; U.S. Pat. No. 5,477,890 to Krummheuer et al.; U.S.Pat. No. 5,508,073 to Krummheuer et al.; U.S. Pat. No. 5,503,197 toBower et al.; and U.S. Pat. No. 5,704,402 to Bowen et al. A two-weaveconstruction airbag cushion is exemplified in U.S. Pat. No. 5,651,395 toGraham et al. but does not discuss the importance of narrow basket-weavesingle fabric layers.

[0081] As will be appreciated, the permeability of an airbag cushionstructure is an important factor in determining the rate of inflationand subsequent rapid deflation following the impact event. Differentairbag cushions are utilized for different purposes. For instance, someairbag cushions are installed within inflation modules for driverprotection within the steering column of an automobile. Others areutilized as protection for front seat passengers and are installed inand around the glove compartment and/or on the dashboard in front ofsuch a passenger seat. Still others have been developed in an effort toprotect all passengers during a long-duration impact event, such as, forexample, a rollover collision. In those types of crashes, the targetairbag cushion must inflate quickly under high pressure (such as betweenabout 10 and 40 psi) and remain inflated at a relatively high pressuresin order to provide the greatest degree of protection to suchpassengers.

[0082] Furthermore, such long-duration airbag cushions preferablycomprise “pillow” formations created through the attachment of at leasttwo different fabrics or fabric ends together and sealed, sewn, or thelike, together. Upon inflation the free space between the attachmentpoints inflate as well, thereby producing the desired cushioned “pillow”structures. Such long-duration, “pillowed” structures have beendisclosed in the prior art as airbag cushions within U.S. Pat. No.5,788,270 to Halano. However, in order to provide a suitable, effectiveairbag fabric and cushion comprising two or more points of attachmentbetween fabrics or fabric ends, there has been a need to improve uponthe structural integrity of the seams at such attachment points toprevent unwanted and potentially harmful leakage of gas or air fromwithin the target airbag cushion. The prior art has discussed thedevelopment of coatings to place over the sewn seams at such attachmentpoints in order to seal the potentially loose portions of such seamsand/or to keep the individual yarns of the airbag fabrics at theattachment points stationary in order to prevent yarn shifting and thuspossible openings for air or gas leakage. However, such coatings areactually supplemental to the seam structures in providing the necessarybarrier to air or gas. A strong, effective, efficient weave constructionis the primary method of initially producing an effective airbag fabricfor incorporation within an airbag cushion.

[0083] Previous attempts have been made at producing inflatable fabricscomprising “pillowed” chambers (such as for side curtains, and the like)which have been produced solely through a weaving procedure and whichexhibit reduced air permeability within their weave constructions (inother words, fabrics which are not sewn together to form an inflatablestructure). For instance, U.S. Pat. No. 5,011,183 to Thornton et al.discloses an inflatable fabric structure comprising at least twodifferent areas of differing fabric layers. Patentees discuss two layersof fabric produced by a plain weave and single layer constructions of aplurality of different weave patterns. The interface between the twodifferent fabric layer areas must exhibit at least three differentfabric densities (which are dictated by weave constructions), whereinthe two looser constructions (double layer plain weave and single layerbasket weave) are separated by a tighter construction (single layerplain weave). Such an overall inflatable fabric structure may possessthe necessary air permeability characteristics required for properfunctioning within a side curtain airbag cushion (particularly uponcoating with a standard airbag coating composition); however, thenumerous differences in fabric densities also place varying pressuresupon discrete areas of the fabric (particularly at or near the interfacebetween the differing fabric layer areas) such that yarn shifting willmost likely occur during an inflation event which may producediscontinuities in the integrity of the coating which may in turncompromise the long-term air permeability required for certain airbagapplications.

[0084] Attempts have been made at improving on such a fabric; howeverthese have led to an increase in the number of different fabric densityareas on the fabric, rather than reducing such differing densities. Forexample, a plain weave construction has been utilized within the doublelayer area, adjacent to a transition weave pattern, which connects withan Oxford weave pattern, and then either a basket-weave or plain weaveconstruction for the remainder of the single layer area on the fabric.Such a complicated scheme is difficult to produce on a weavingapparatus, as an initial problem. Secondly, the utilization of an Oxfordweave zone has been utilized in an attempt to prevent the possibility ofweaving in a plain pattern (which is highly undesirable due to thedifficulty in manufacturing such high density single-layers fabrics fromdouble-layer amounts of yarn). However, if the area of single layer offabric is not substantially a straight line, and thus must follow acurved structure, the Oxford weave will eventually become a plain weavefor at least that area around such a curved seam. In such an instance,the interface between the two differing layers of fabric will beirregular and invariably produce an undesirable and/or irregular numberof floats (i.e., yarns which pass either over or under a certain numberof perpendicularly oriented yarns; greater than three such orientedyarns would produce difficulties in preventing yarn shifting, as merelyone example). As such, the resultant fabric is itself highly undesirableas a barrier to air permeability, even though coatings may be applied toincrease such performance. Thirdly, the individual yarns at the seambetween the double and single layer areas, will be placed upontremendous strain during an inflation event and, as in the Thornton etal. teaching, will most likely result in yarn shifting. With suchshifting yarns, the permeability benefits, if any, would, again, mostlikely be compromised and the produced airbag fabric would not functionas required.

[0085] In view of the foregoing, it is preferred to provide aninflatable all-woven fabric having all-basket-woven seams at thesingle/double layer interfaces within the fabric. It is even morepreferred to provide an all-woven inflatable fabric with double layerzones of fabric and single layer zones of fabric (to form “pillowed”chambers) which comprises at most two different fabric densitiesthroughout the entire fabric structure. Also, an object of thisinvention is for the utilization of such inflatable fabrics as airbagcushions within a vehicle restraint system. The term “vehicle restraintsystem” is intended to mean both inflatable occupant restraining cushionand the mechanical and chemical components (such as the inflation means,ignition means, propellant, and the like).

[0086] To achieve these and other objects and in accordance with thepurpose of the invention, as embodied and broadly described herein, atleast one embodiment of the invention provides an inflatable fabriccomprising at least two layers of fabric in certain discrete areas ofthe fabric and at least one single fabric layer at a discrete areawithin said fabric, wherein said at least one single fabric layer isformed, for example, from a basket weave pattern of an even number ofyarns; preferably, the weave structure for said single layer fabrics isa 2×2 basket weave pattern, for example, from 4 to 8 yarns in length.Also, this invention encompasses an inflatable fabric comprising atleast two layers of fabric in certain discrete areas of the fabric andat least one single fabric layer at a discrete area within said fabric,wherein the weave diagram for such a fabric does not exhibit more thanthree consecutive filled or unfilled blocks in any row or column.Furthermore, this invention also concerns an inflatable fabriccomprising at least two layers of fabric in certain discrete areas ofthe fabric and at least one single fabric layer at a discrete areawithin said fabric, wherein only two separate weave densities arepresent within the entire fabric structure.

[0087] The term “inflatable fabric” is intended to encompass any fabricwhich is constructed of at least two layers of fabric which can besealed to form a bag article. The inventive inflatable fabric thus mustinclude double layers of fabric to permit such inflation, as well assingle layers of fabric either to act as a seal at the ends of suchfabric panels, or to provide “pillowed” chambers within the targetfabric upon inflation. The term “all-woven” as it pertains to theinventive fabric thus requires that the inflatable fabric having doubleand single layers of fabric be produced solely upon a loom. Any type ofloom may be utilized for this purpose, such as water-jet, air-jet,rapier, dobby, and the like. Jacquard weaving and dobby weaving,however, are most preferred.

[0088] The constructed fabric may exhibit balanced or unbalancedpick/end counts; the main requirement in the woven construction is thatthe single layer areas of the inflatable fabric exhibit solelybasket-weave patterns. These patterns are made through the arrangementof at least one warp yarn (or weft yarn) configured around the same sideof two adjacent weft yarns (or warp yarns) within the weave pattern. Theresultant pattern appears as a “basket” upon the arrangement of the samewarp (or weft) yarn to the opposite side of the next adjacent weft (orwarp) yarn. Such basket weave patterns may include the arrangement of awarp (or weft) yarn around the same side of any even number of weft (orwarp) yarns, preferably up to about six at any one time.

[0089] The utilization of such basket weave patterns in the single layerzones provides a number of heretofore unexplored benefits withininflatable fabric structures. For example, such basket weave patternspermit a constant “seam” width and weave construction over an entiresingle layer area, even where the area is curved. As noted above, thestandard Oxford weaves currently utilized cannot remain as the sameweave pattern around curved seams; they become plain weave patterns.Also, such basket weave seam patterns permit the construction of aninflatable fabric having only plain woven double layer fabric areas andsingle layer “seams” with no “floats” of greater than three picks withinthe entire fabric structure. Such a fabric would thus not possessdiscrete locations where the air permeability is substantially greaterthan the remaining portions of the fabric. Generally, the prior art(such as Thornton et al., supra) produce floats of sometimes as much assix or seven picks at a time. Although available software to the weavingindustry permits “filling in” of such floats within weave diagrams, sucha procedure takes time and still does not continuously provide a fabricexhibiting substantially balanced air permeability characteristics overthe entire structure. The basket-weave formations within the singlefabric layers thus must be positioned in the fabric so as to preventirregularities (large numbers of floats, for example) in the weaveconstruction at the interface between the single and double fabriclayers (as described in FIG. 10, below). Another benefit such basketweave patterns accord the user is the ability to produce more than onearea of single layer fabric (i.e., another “seam” within the fabric)adjacent to the first “seam.” Such a second seam provides a manner ofdissipating the pressure from or transferring the load upon eachindividual yarn within both seams. Such a benefit thus reduces thechances of deleterious yarn shifting during an inflation event throughthe utilization of strictly a woven fabric construction (i.e., notnecessarily relying upon the utilization of a coating as well). Thepreviously disclosed or utilized inflatable fabrics having both doubleand single fabric layer areas have not explored such a possibility inutilizing two basket-weave pattern seams. Furthermore, such a two-seamconstruction eliminates the need for weaving a large single fabric layerarea within the target inflatable fabric. The prior art fabrics whichproduce “pillowed” chambers for airbag cushions (such as side curtains),have been formed through the weaving of entire areas of single fabriclayers (which are not actually seams themselves). Such a procedure istime-consuming and rather difficult to perform. The inventive inflatablefabric merely requires, this alternative embodiment, at least two verynarrow single fabric layer areas (seams) woven into the fabric structure(another preferred embodiment utilizes merely one seam of single layerfabric); the remainder of the fabric located within these two areas maybe double layer if desired. Thus, the inventive fabric permits animproved, cost-effective, method of making a “pillowed” inflatablefabric.

[0090] The inflatable fabric itself is preferably produced fromall-synthetic fibers, such as polyesters and polyamides, althoughnatural fibers may also be utilized in certain circumstances.Preferably, the fabric is constructed of nylon-6,6. The individual yarnsutilized within the fabric substrate must generally possess denierswithin the range of from about 40 to about 840; preferably from about100 to about 630.

[0091] As noted above, coatings should be applied to the surface as anecessary supplement to the air permeability, abrasion resistance and/orpuncture resistance of the inventive fabric. Since one preferredultimate use of this inventive fabric is as a side curtain airbag whichmust maintain a very low degree of air permeability throughout acollision event (such as a rollover where the curtain must protectpassengers for an appreciable amount of time), a decrease in permittedair permeability is highly desirable. Any standard coating, such as asilicone, polyurethane, polyamide, polyester, rubber (such as neoprene,for example), and the like, may be utilized for this purpose and may beapplied in any standard method and in any standard amount on the fabricsurface.

[0092] Furthermore, although it is not preferred, it has been found thatthe inventive coating composition provides similar low permeabilitybenefits to standard one-piece woven airbags, particularly with theinventive add-on amounts of high tensile strength, high elongation,non-silicone coatings; however, the amount of coating required to permithigh characteristic leak-down times is much higher than for theaforementioned Sollars, Jr. inventive one-piece woven structure. Thus,add-on amounts of as much as 1.5 or more ounces per square yard may benecessary to effectuate the proper low level of air permeability forthese other one-piece woven airbags. Even with such higher add-oncoatings, the inventive coatings themselves clearly provide a markedimprovement over the standard, commercial, less preferred silicone,etc., coatings (which must be present in amounts of at least 3.0 ouncesper square yard).

[0093] Additionally, it has also been found that the inventive filmcoating compositions, at the inventive add-on amounts, etc., provide thesame types of benefits with the aforementioned sewn, stitched, etc.,side curtain airbags. Although such structures are highly undesirabledue to the high potential for leakage at these attachment seams, it hasbeen found that the inventive coating provides a substantial reductionin permeability (to acceptable characteristic leak-down time levels, infact) with correlative lower add-on amounts than with standard siliconeand neoprene rubber coating formulations. Such add-on amounts mayapproach about 2.7 ounces per square yard or more, but lower amountshave proven effective (2.2 ounces per square yard, for example)depending on the utilization of a sufficiently high tensile strength andsufficiently stretchable elastomeric component within the film coatingcomposition directly in contact with the target fabric surface. Again,with the ability to reduce the amount of coating materials (which aregenerally always quite expensive), while simultaneously providing asubstantial reduction in permeability to the target airbag structure, aswell as high resistance to humidity and extremely effective agingstability, the inventive coating composition, and the inventive coatedairbag itself is clearly a vast improvement over the prior airbagcoating art.

[0094] Another aspect of this invention, is the ability to pack thecoated airbag cushions within cylindrical storage containers at the roofline of a target automobile in as small a volume as possible. In arolled configuration (in order to best fit within the cylindricalcontainer itself, and thus in order to best inflate upon a collisionevent downward to accord the passengers sufficient protection), theinventive airbag may be constricted to a cylindrical shape having adiameter of about 24 millimeters or more. In such an instance, with a 2meter long cylindrical roofline storage container, the necessary volumeof such a container would equal about 855 cm³ or more (with the volumecalculated as 2[Pi]radius²). Standard rolled packing diameters are atleast 25 millimeters for commercially available side curtain airbagcushions (due to the thickness of the required coating to provide lowpermeability characteristics). Thus, the required cylindrical containervolume would be at least 980 cm³. Preferably, the rolled diameter of theinventive airbag cushion during storage is about 21 millimeters or more(giving a packed volume of about 647 cm³ or more). In relation, then, tothe depth of the airbag cushion upon inflation (i.e., the length theairbag extends from the roofline down to its lowest point along the sideof the target automobile, such as at the windows), the quotient of theinventive airbag cushion's depth (which is standard at approximately 17inches or 431.8 millimeters) to its rolled packed diameter should be atleast about 18.0 or less. Of course, this range of quotients does notrequire the depth to be at a standard of 17 inches, and is primarily afunction of coating thickness, and thus add-on weight.

[0095] Also, it has been discovered that any film and/or coating with atensile strength of at least 2,000 psi and an elongation at break of atleast 180% coated onto and over both sides of a side curtain airbagfabric surface at a weight of at most about 10.0 ounces per square yard,and preferably below about 7.0, more preferably below about 6.0, andmost preferably less than about 5.0 ounces per square yard, provides acoated airbag cushion which exhibits extremely low and extendedpermeability upon and after inflation. This unexpectedly beneficial typeand amount of film coating thus provides an airbag cushion which willeasily inflate after prolonged storage and will remain inflated for asufficient amount of time to ensure an optimum level of safety within arestraint system. Furthermore, it goes without saying that the less filmcoating composition required, the less expensive the final product.Additionally, a lower required amount of film coating composition willtranslate into a decrease in the packing volume of the airbag fabricwithin an airbag device. This benefit thus improves the packability forthe airbag fabric.

[0096] One preferred airbag cushion of this invention was produced inaccordance with the following Example:

EXAMPLE

[0097] First, an adhesive primer formulation was produced having thecomposition: Component Parts by weight Desmoderm ® 43195 (BayerCorporaiton, polyurethane 25 grams resin) Dimethylformamide (Aldrich,solvent) 75 grams Desmodur ® CB-75N (Bayer, polyisocyanate adhesion  4grams promoter)

[0098] This primer coating was applied to both sides of a 2.5 liter sizeJacquard woven nylon airbag (of 440 denier fibers), made in accordancewith the Figures and preferred embodiments within U.S. patentapplication Ser. No. 09/406,264, to Sollars, Jr., previouslyincorporated by reference. The primer coating was dried at about 160° C.for about 2 minutes to obtain a dry coating weight of about 0.25 ouncesper square yard on each side. Subsequently, a 2 mil thick polyurethanefilm (Dureflex™ PT9400) was then laminated on both sides of the primercoated airbag utilizing a hotpress providing about 80 psi press pressureat about 188° C. with a residence time of about 1 minute. The totalpolyurethane film add-on weight on each side of the airbag was about 2.2ounces per square yard. The airbag was then rapidly inflated to 30 psiair pressure. More than 28 seconds elapsed before the air pressureleaked down to 8 psi. The leakage rate was thus measured at 10 psi to beabout 4 SCFH. The characteristic leak-down time was an astoundingamount, greater than 80 seconds.

[0099] As depicted in FIG. 1, an interior of a vehicle 10 prior toinflation of a side curtain airbag is shown. The vehicle 10 includes afront seat 12 and a back seat 14, a front side window 16 and a back-sidewindow 18, a roofline 20, within which is stored a cylindrically shapedcontainer 22 housing the inventive side curtain airbag 26. Also presentwithin the roofline 20 is an inflator assembly 24 which ignites andforces gas into the side curtain airbag 26 upon a collision event.

[0100]FIG. 2 shows the inflated side curtain airbag 26. As noted above,the airbag 26 may be coated with a coating formulation and/or film,preferably polyurethane polycarbonate. The inventive airbag 26 willpreferably remain sufficiently inflated for at least 5 seconds, andpreferably as high as at least 20 seconds.

[0101]FIG. 3 shows the side curtain airbag 26 prior to or after storagein its uninflated state within the roofline cylindrically shapedcontainer 22. The thickness of the airbag 26, measured as the rolledpacking diameter (as in FIG. 5, below) as compared with the depth of theairbag measured from the roofline cylindrically shaped container 22 tothe bottom most point 28 of the airbag 26 either in its uninflated orinflated state should preferably be at least 17 and at most 29, as notedabove.

[0102]FIGS. 4 and 5A aid in understanding this concept through theviewing of the rolled airbag 26 as stored within the container 22 alongline 5-5. The diameter measurement of the airbag 26 of the exampleabove, is roughly 24 millimeters 9 or more. The standard depth of sidecurtain airbags is roughly 17 inches, or about 431.8 millimeters.

[0103]FIGS. 3 and 6 show the respective interior and exterior surfaces102, 104 of the airbag 26.

[0104]FIGS. 5A shows the airbag 26 being rolled. Alternatively, FIG. 5Bshows the airbag 26 being folded. The airbag 26 may be rolled or foldedand packed into a cylindrical woven or molded tube, or the airbag 26 maybe folded and held in position by straps such as breakaway moldedplastic straps.

[0105] With reference to FIGS. 7-9 of the drawings, and in accordancewith selected embodiments of the present invention providing abrasionresistant fabrics and/or airbag cushions, resistance to abrasion bygravel (FIG. 7) was tested by using road side gravel placed on a testboard, inflating a test bag to 10 psi, placing the test board on theinflated bag with the gravel toward the bag and loading the test boardwith a 13 lbs. concrete block, scrubbing the gravel board across the bagat one cycle per second, and measuring the gas flow rate required tomaintain bag pressure at 10 psi. As shown in FIG. 7 of the drawings, abag in accordance with the present invention (test bag) had an extremelyhigh resistance to abrasion by gravel in that the pressure required tomaintain bag pressure at 10 psi increased only slightly during theinitial phase of the testing and then remained relatively constant fromabout 20 to 100 cycles. In contrast to the test bag of the presentinvention, the base line bag showed a steady increase from 0 to 20cycles and then a drastic increase in pressure to maintain bag pressureat 10 psi from 20 to about 25 cycles.

[0106] The test bag was a jacquard woven airbag made of 420 denier hightenacity nylon, coated with 1.2 oz/yd² polyurethane on each side, and a3 mil thick Duraflex PT 9400 polyurethane film was laminated on one sideof the bag (FIG. 12B).

[0107] The baseline bag was a jacquard woven airbag made from 420 denierhigh tenacity nylon coated with 4 oz/yd² of silicone on each side of thebag.

[0108] With reference to FIG. 8 the drawings and resistance to abrasionby concrete, testing of a test bag in accordance with the presentinvention entailed using a concrete block as the test media, inflating atest bag to 10 psi, placing a concrete block on the inflated bag (about13 lbs.), scrubbing the concrete block and forth across the bag at onecycle per second and measuring the flow rate required to maintain bagpressure at 10 psi. As shown in FIG. 8 of the drawings, the test bag ofthe present invention showed a high resistance to abrasion by concreteand had a very low and constant leak rate from 0 to 100 cycles. Incontrast to the test bag of the present invention, the base line bag hada higher leak rate which increased from 0 to about 12 cycles anddrastically increased from about 12 to 20 cycles.

[0109] The test bag was a jacquard woven airbag made of 420 denier hightenacity nylon, coated with 1.2 oz/yd² polyurethane on each side, andwith a 3 mil thick Duraflex PT 9400 polyurethane film was laminated onone side of the bag (FIG. 12B).

[0110] The baseline bag was a jacquard woven airbag made from 420 denierhigh tenacity nylon coated with 4 oz/yd² of silicone on each side of thebag.

[0111] With reference to FIG. 9 of a drawing, the test bag of thepresent invention showed a very high resistance to puncture as comparedto a baseline bag. Testing of the test bag of the present invention forpuncture included placing shards of vehicle side window glass on aplate, deploying the test bag to 30 psi against the plate covered withthe broken glass, dropping a 25 pound weight on the bag as the bagreached full inflation to force the inflated bag to impact the brokenglass, and measuring the time for the pressure to fall from 30 psi to 15psi (time to lose half of full pressure). As shown in FIG. 9 of thedrawings, the test bag of the present invention took at least about 5seconds to lose half of its pressure to drop from (30 psi to 15 psi). Incontrast, the base line bag took less than one half of a second.

[0112] The test bag was a jacquard woven airbag made of 420 denier hightenacity nylon, coated with 1.2 oz/yd² polyurethane on each side, with a3 mil thick Duraflex PT 9400 polyurethane film laminated on one side ofthe bag, and with a layer of lightweight polyester airbag fabric overthe film (FIG. 12D).

[0113] The baseline bag was a jacquard woven airbag made from 420 denierhigh tenacity nylon coated with 4 oz/yd² of silicone on each side of thebag.

[0114] Hence, the test bags of the present invention showed anunexpectedly high resistance to abrasion by gravel, unexpectedly highresistance to abrasion by concrete, and an unexpectedly high resistanceto puncture. Such features find special applicability in a side curtainairbag which is to provide rollover protection.

[0115] Turning now to FIGS. 10 and 11 of the drawings, in FIG. 10 thereis shown a cross-section of a preferred structure for the double fabriclayers 52, 54, 58, 60, 64, 66 and single fabric layers 56, 62 of theinventive inflatable fabric 50. Weft yarns 68 are present in each ofthese fabric layer areas 52, 54, 56, 58, 60, 62, 64, 66 over and underwhich individual warp yarns 78, 80, 82, 84 have been woven. The doublefabric layers 52, 54, 58, 60, 64, 66 are woven in plain weave patterns.The single fabric layers 56, 62 are woven in basket weave patterns. Fourweft yarns each are configured through each repeating basket weavepattern within this preferred structure; however, two or more weft yarnsmay be utilized within these single fabric layer areas (seams) 56, 62.The intermediate double fabric layer areas 58, 60 comprise each onlyfour weft yarns 68 within plain weave patterns. The number of suchintermediate weft yarns 68 between the single fabric layer areas 56, 62must be in multiples of two to provide the maximum pressure bearingbenefits within the two seams 56, 62 and thus the lowest possibility ofyarn shifting during inflation at the interfaces of the seams 56, 62with the double fabric layer areas 52, 54, 64, 66.

[0116]FIG. 11 shows the weave diagram 70 for an inventive fabric whichcomprises two irregularly shapes concentric circles as the seams. Such adiagram also provides a general explanation as to the necessaryselection criteria of placement of basket-weave patterns within thefabric itself. Three different types of patterns are noted on thediagram by different shades. The first 72 indicates the repeated plainweave pattern throughout the double fabric layers (52, 54, 58, 60, 64,66 of FIG. 10, for example) which must always initiate at a location inthe warp direction of 4X+1, with X representing the number of pickarrangement within the diagram, and at a location in the fill directionof 4X+1 (thus, the pick arrangement including the specific two-layerplain-weave-signifying-block 72 begins at the block four spaces below itin both directions). The second 74 indicates an “up-down” basket weavepattern wherein an empty block must exist and always initiate thebasket-weave pattern at a location in the warp direction of 4X+1, with Xrepresenting the number of repeating pick arrangements within thediagram, and at a location in the fill direction of 4X+1, when a seam(such as 56 and 62 in FIG. 10) is desired (thus, the pattern includingthe pertinent signifying “up-down” block 74 includes an empty blockwithin the basket-weave pick arrangement in both the warp and filldirections four spaces below it). The remaining pattern, which isbasically a “down-up” basket weave pattern to a single fabric layer(such as 56 and 62 in FIG. 10) is indicated by a specifically shadedblock 76. Such a pattern must always initiate at a location in the warpdirection of 4X+1 and fill of 4X+3, or warp of 4X+3 and fill of 4X+1,when a seam is desired. Such a specific arrangement of differing“up-down” basket weave 74 and “down-up” basket weave 76 pattern isnecessary to effectuate the continuous and repeated weave constructionwherein no more than three floats (i.e., empty blocks) are presentsimultaneously within the target fabric structure. Furthermore, again,it is believed that there has been no such disclosure or exploration ofsuch a concept within the inflatable fabric art.

[0117] With reference to FIGS. 3 and 6, the side curtain airbag orcushion 26 has an interior surface 102 (close to the occupant) and anexterior surface 104 facing the window or windows. With reference toFIG. 10, a thick coating, layer, film, or the like 86 represents theexterior surface (window side) of the airbag 50 while a thinner coating,film, layer, or the like 88 represents the interior surface (occupantside) of the airbag.

[0118] A side curtain type of air bag acts as a safety barrier betweenthe occupant of a vehicle and hazards outside of the vehicle in acollision. Puncture resistance is preferred to prevent prematureleak-down and possible bag rupture due to impact on sharp objects suchas broken window glass, nails, splintered wood, rocks and gravel withsharp edges, broken plastic or torn metal generated in a vehicle crash.Bag puncture may result in loss of bag gas pressure necessary to providethe cushioning and energy absorbing function of the air bag, andtherefore loss of safety provided by the air bag.

[0119] The side curtain air bag may get between the occupant and anothervehicle or other outside object such as a utility pole in a side impactaccident. The air bag may also hit the ground and other objects on theground in a rollover type of collision. Side impact air bags, especiallyrollover protection curtain type air bags are designed to protect theoccupants in those types of accidents.

[0120] Side impact air bags are usually made of coated fabric to providequick inflation (20-40 ms) to operating pressure for a relatively longertime compared to a typical driver side air bag. For rollover protection,the air bag needs to stay inflated at relatively high pressure for anextended period of time (several seconds). Even a small puncture in thecoating by a small sharp object can greatly lower the gas pressure inthe bag and sacrifice the bag performance. There are also situationswhere part of the bag can hit against one or more small sharp objects.Due to great bag pressure and such a small contact area, the fabric mayget cut through, and even cause the bag to burst on impact.

[0121] We have experimented with many fabric designs and fabriccombinations and found a surprising correlation between the air bagpuncture resistance under simulated crash conditions and two differentASTM standard puncture resistance tests. We have also found that certainfabric structures and treatments provide unexpectedly good punctureresistance.

[0122] We have constructed different fabric structures for the sidecurtain airbag and experimented with the bag performance in punctureresistance tests. Compared to current air bag constructions, we havedemonstrated great improvement in puncture resistance. Additionally, wehave found that a combination of two ASTM tests can provide a goodcorrelation to puncture under simulated crash conditions.

[0123] A test was devised to study side impact bag performance undersimulated crash conditions. Two plates that simulate the sharp objectstypically encountered in an automotive accident were constructed (aglass plate and a gravel plate). On the glass plate, pieces of brokenglass from a car side window were fixed on a flat thick plywood surfaceusing epoxy resin. On the gravel plate, road construction gravel havingstones with relatively sharp edges was fixed onto a thick plywoodsurface using asphalt. In the test, a plate is horizontally fixed on astable platform. A side curtain type air bag positioned a couple ofinches above the plate is inflated at a fast rate (about 30 ms to itspeak pressure). Immediately after inflation, a 25 lb. weight is droppedfrom a 5½ feet height onto the top side of the air bag. The droppedweight thus pushes the fully inflated airbag down against the plate withthe sharp objects. The gas pressure inside the air bag is monitored andthe rate of pressure decay reflects the damage to the bag. As the rateof pressure decay is approximately exponential, the “half life”—the timefor the pressure to drop to one half its initial pressure—is a simplemeasure of the degree of damage to the bag. Tested bags were alsoexamined to determine the failure mode, namely, number of smallpunctures and large holes. Small punctures are those that result in gasleakage due to a break in the coating with 2 or fewer yarn breaks. Largeholes are those that involve multiple yarn breaks, cuts, or localizedburst or tear. TABLE I Test results of impact drop test of bags A-K onbroken glass plate using inflation simulator. Poly- Silicone Siliconeure- coat- coating thane 420 d ing - with coat- 420 d lami- S/1125S/1125 Bag 1 nonwoven ed sewn nate sewn laminate struct. A B C D E F GHalf <0.3 0.3 0.3-2 5 0.5 5 Life Sec Big 22 16 9 3 0 3 1 holes Small 4 25 2 2 4 2 holes 630 d 630 d 100 d 100 d sewn laminate sewn laminate Bagstruct. H I J K Half Life — 18 0.7 10 Sec Big holes 0 0 2 0 0 Small 1 01 1 holes Scratches 0 Other observ.

[0124] Big holes: holes that have fabric tear and/or multiple yarn cutor bursting, contribute to rapid leak down and major failure.

[0125] Small holes: small pin holes that do not have any fabric tear orhave only 1 or 2 broken yarns. Relatively small amount of air leaksthrough the small pin holes.

[0126] Half Life: time in sec. required for pressure in bag to drop by ½of the peak pressure.

[0127] ASTM F 1342 “Standard Test Method for Protective ClothingMaterial Resistance to Puncture” provides a good measure regarding howeasily a sharp object can penetrate a fabric structure. ASTM D 4833“Standard Test Method for Index Puncture Resistance of Geotextiles,Membranes, and Related Products” provides a good measure of how easily afabric would burst at high stress concentration on a small contact area.We have found that ASTM F 1342 test method gives a good indication offabric resistance to initial penetration by a sharp object and that ASTMD 4833 test method relates largely to the resistance to local burstingand tear.

[0128] ASTM D 4833—Standard Test Method for Index Puncture Resistance ofGeotextiles, Geomembranes and Related Products.

[0129] A text specimen is clamped without tension between circularplates of a ring clamp attachment secured in a tensile testing machine.A force is exerted against the center of the unsupported portion of thetest specimen by a solid steel rod attached to the load indicator untilrupture of the specimen occurs. The maximum force recorded is the valueof puncture resistance of the specimen.

[0130] ASTM F 1342—Standard Test Method for Protective Clothing MaterialResistance to Puncture.

[0131] A material specimen is placed in a stationary support assemblythat is in turn affixed to the lower arm of a tensile testing machine. Asharp puncture probe of set dimension is moved at a constant velocityuntil the material specimen is punctured. The force required to puncturethe material specimen is measured by the compression cell and theaverage force is reported as the measure of resistance to puncture.TABLE II Test results: A. Uncoated single layer fabric 420 630Polyester, denier, denier, 78 denier 100 denier Spun laced 49 × 49 40 ×40 96 × 96 110 × 110 non-woven Fabric (420 d) (630 d) (PET 78) (100 d)fabric ASTM 2-6 6.9 3.3 9.7 1.5 Puncture force (LB) ASTM 174 218 43.3118 Index puncture, LB B. Coated fabric, single layer 420 420 denier,denier, 49 × 49 420 denier, 420 denier, 630 denier 49 × 49 silicone, 494× 49 47 × 48 40 × 40 HC LR* polyurethane Polyamide HC silicone siliconeFabric coating coating coating coating coating ASTM 5 8 6 3 3 Punctureforce ASTM 151 198 159 153 144 Index puncture  LR — liquid rubberresin, HG — high consistency rubber resin C. 2 layers structure,uncoated fabric over coated fabric S/1125 fabric 420 d over 420 d over630 d over over polyurethane silicone polyurethane polyurethane Fabriccoated 420 d coated 420 d coated 420 d coated 420 d, ASTM 15.6 12 18.011.8 Puncture force LB ASTM Index 348 393 253 puncture force LB D.Laminated 2 layer structures Non- Non- woven woven 420 d lami- lami-lami- nated 2 mil nated nated to a S/1125 poly- to 420 d sili- 100 d 210d fabric 630 d film 420 d using cone lami- lami- lami- lami- lami- usingpoly- coated nated nated nated nated nated poly- ure- 420 d to to to toto ure- Fabric thane fabric 420 d 420 d 420 d 420 d 420 d thane ASTM 266.2 25 21.8 16.6 26.9 8.6 13.2 punc- ture force (LB) ASTM 350 206 325326 240 385 229 index punc- ture force (LB) # provided better protectionthan uncoated fabric because the coating links the yarns and fiberstogether to effectively alleviate stress concentration and to providebetter resistance to sharp object's penetration through yarninterstices.

[0132] With reference to FIGS. 12A-12M of the drawings, schematiccross-sectional layer diagrams of selected embodiments of the side wallof an airbag or airbag cushion toward the window are shown. Withparticular reference, FIG. 12A shows an airbag fabric having a coatingon the exterior surface thereof.

[0133]FIG. 12B shows a coated airbag fabric having a film laminated orotherwise adhered thereto with the coating between the film and fabric.

[0134]FIG. 12C illustrates a coated airbag fabric having an outer fabriclayer laminated or otherwise adhered thereto with the coating betweenthe inner and outer fabric layers.

[0135]FIG. 12D represents a multi-layered airbag laminate orconstruction (such as shown in FIG. 12B) including a coated airbagfabric and a film laminated thereto with the addition of an outer fabriclayer laminated or otherwise adhered to the film layer of the laminateor composite.

[0136]FIG. 12E shows an airbag fabric having a film laminated or adheredthereto.

[0137]FIG. 12F shows an airbag fabric having a primer applied theretoand then a coating over the primer.

[0138]FIG. 12G shows a multi-layer fabric, laminate or constructionincluding a first airbag fabric laminated or adhered to a second orouter fabric by an adhesive.

[0139]FIG. 12H represents a multi-layer airbag fabric, composite orlaminate including a first airbag fabric layer, a coating, a second orouter fabric layer, and a coating or film atop the second fabric layer.

[0140]FIG. 12I illustrates a multi-layer airbag fabric, composite orlaminate including a first layer of airbag fabric having an innercoating or film and an outer coating, primer or adhesive with a coating,fabric or film adhered to the upper surface of the outer coating, primeror adhesive.

[0141]FIG. 12J represents a multi-layer airbag fabric, composite,laminate, or the like having an airbag fabric with a coating, primer, oradhesive layer above and below and a film located below the lowercoating, primer, or adhesive layer and a coating, fabric or film locatedabove the upper coating, primer, or adhesive layer.

[0142]FIG. 12K shows an airbag fabric having a separate film layerlocated below or adjacent the inner surface of the airbag fabric.

[0143]FIG. 12L represents an airbag fabric having a separate barrierlayer located above or adjacent to the outer surface of the airbagfabric.

[0144]FIG. 12M illustrates an airbag fabric having a coating or filmadhered thereto in a fashion producing multiple individual cells orpockets.

[0145] FIGS. 12I-12K are directed to, for example, bag-in-bagconstructions wherein an inner coating and/or film forms an inflatablecavity in the airbag.

[0146] The exact construction of the airbag or side walls thereof of thepresent invention is not necessarily limited, but is intended to coverall such constructions which provide the desired puncture resistanceand/or abrasion resistance as well as other desired properties of theairbag.

[0147] The inner or lower fabric layer of FIGS. 12A-12M is preferablywoven airbag fabric and more preferably may be jacquard or dobby wovenairbag fabric of a woven one piece airbag. The outer or upper fabriclayer of FIGS. 12C, 12D, 12G, 12H, 12I, 12J, or 12K is preferably wovenairbag fabric.

[0148] The barrier of FIG. 12L is preferably a material which ispuncture and/or abrasion resistant such as a textile material, fabric,or the like.

[0149] There are, of course, many alternative embodiments andmodifications of the present invention which are intended to be includedwithin the spirit and scope of the following claims. While the inventionis described and disclosed in connection with certain preferredembodiments and practices, it is in no way intended to limit theinvention to those specific embodiments, rather it is intended to coverequivalent structures structural equivalents and all alternativeembodiments and modifications as may be defined by the scope of theappended claims and equivalents thereto.

What we claim is:
 1. A fabric adapted for use in airbag cushions,especially side curtain airbags providing rollover protection,comprising: an airbag fabric having at least one coating, film, fabricor layer on the exterior surface thereof, having at least one ofabrasion resistance, puncture resistance, and combinations thereof, andhaving an ASTM D 4833 index puncture resistance greater than about 210lbs. and ASTM F 1342 puncture resistance greater than about 10 lbs.
 2. Afabric adapted for use in airbag cushions, especially side curtainairbags providing rollover protection, comprising: an airbag fabriccovered with a film layer, wherein said fabric is adapted for use in anairbag having a characteristic leak-down time after inflation of atleast 5 seconds.
 3. A fabric adapted for use in airbag cushions,especially side curtain airbags providing rollover or impact protection,comprising: an airbag fabric having at least one of a woven and knitfabric laminated to the exterior surface thereof.
 4. An airbag fabrichaving an ASTM D 4833 index puncture resistance greater than about 210lbs. and ASTM F 1342 puncture resistance greater than about 10 lbs.
 5. Apuncture resistant airbag fabric comprising at least two layers offabric, with at least one layer being coated airbag fabric and the otherbeing a woven or knitted fabric.
 6. A puncture resistant airbag fabriccomprising at least two laminated layers of fabric adapted for use onthe side of an airbag facing the outside of a vehicle when inflated. 7.The fabric as recited in at least one of claims 1 and 5, wherein saidcoating is at least one polymer elastomer, or the like such as siliconeor polyurethane.
 8. The fabric as recited in claim 1, wherein thecoating, film or layer further includes a polyurethane film laminated orplaced over the coated fabric.
 9. The fabric as recited in claim 1,wherein the coating, film or layer further includes an outer layer offabric laminated over the coated fabric.
 10. The fabric as recited inclaim 9, wherein the fabric is laminated using an elastomeric coating,film, adhesive, or combination thereof.
 11. The fabric as recited in atleast one of claims 3, 5, 6, and 9, wherein said outer layer of fabricis constructed of at least one of polyester, polyamide, polyolefin,polyurethane, or combinations thereof.
 12. An airbag cushion comprisingthe fabric of at least one of claims 1, 2, 3, 4, 5, and 6 on at leastthe exterior surface thereof.
 13. The airbag cushion of claim 12,wherein said fabric is coated with a laminate film, and wherein saidairbag cushion exhibits a characteristic leak-down time after inflationof at least 5 seconds.
 14. The airbag cushion of claim 13, wherein saidfilm is silicone free.
 15. The airbag cushion of claim 13, wherein saidfilm comprises polyurethane, polyamide, or copolymer elastomers.
 16. Theairbag cushion of claim 13, wherein said coated fabric is woven frompolyamide yarns.
 17. The airbag cushion of claim 16, wherein saidpolyamide yarns are formed from nylon 6,6 fiber.
 18. The airbag cushionof claim 16, wherein said polyamide yarns are multifilament yarnscharacterized by a linear density of about 210-630 denier.
 19. Theairbag cushion of claim 18, wherein said multifilament yarns arecharacterized by a filament linear density of about 7 denier perfilament or less.
 20. The airbag cushion of claim 13, wherein said filmis present on said airbag fabric surface in an amount of about 0.5 to10.0 mils thick or ounces per square yard.
 21. The airbag cushion ofclaim 20, wherein said film is present on said airbag fabric in athickness of at most 5 mils or in an amount of at most 5 ounces persquare yard.
 22. The airbag cushion of claim 12, wherein said fabric iscoated with a film layer; wherein said film possesses a tensile strengthof at least 2,000 psi and an elongation at break of at least 180%; andwherein said airbag cushion exhibits a characteristic leak-down timeafter inflation of at least 5 seconds.
 23. The airbag cushion of claim22, wherein said film comprises polyurethane.
 24. The airbag cushion ofclaim 22, wherein said coated fabric is woven from polyamide yarns. 25.The airbag cushion of claim 24 wherein said polyamide yarns are formedfrom nylon 6,6 fiber.
 26. The airbag cushion of claim 24, wherein saidpolyamide yarns are multifilament yarns characterized by a lineardensity of about 210-630 denier.
 27. The airbag cushion of claim 26,wherein said multifilament yarns are characterized by a filament lineardensity of about 7 denier per filament or less.
 28. The airbag cushionof claim 22, wherein said film is present on said airbag fabric surfacein a thickness of about 0.5-10.0 mils or an amount of about 0.5-10.0ounces per square yard.
 29. The airbag cushion of claim 22, wherein saidfilm is present coated on said airbag fabric surface in a thickness ofabout 3 mils or an amount of about 3 ounces per square yard.
 30. Aninflatable fabric comprising the fabric of at least one of claims 1, 2,3, 4, 5, and
 6. 31. The fabric as recited in claim 30 wherein there areat least two layers of fabric in certain discrete areas of the fabricand at least one single fabric layer at a discrete area within saidfabric.
 32. The fabric of claim 31 wherein said at least two layers offabric within said inflatable fabric are formed from one type of weavepattern.
 33. The fabric of claim 32 wherein the weave pattern of said atleast two layers of fabric within said inflatable fabric is a plainweave pattern.
 34. The fabric of claim 31 wherein at least two discreteareas of single fabric layers are present within said inflatable fabric,and wherein said at least two single fabric layers are separated by anarea of double layer fabric.
 35. The fabric of claim 34 wherein said atleast two single fabric layer areas are seams through the inflatablefabric which run parallel to each other.
 36. The fabric of claim 34wherein said at least two single fabric layer areas are constructed frombasket weave patterns containing an even number of yarns.
 37. The fabricof claim 34 wherein said separator double fabric layer between said twosingle layers of fabric comprises an even number of weft yarns.
 38. Thefabric of claim 37 wherein said separator double fabric layer comprisesat most 12 weft yarns and at least 2 weft yarns.
 39. The fabric of claim38 wherein said at least two single fabric layers are constructed solelyfrom two-by-two basket weave patterns and said separator double fabriclayer comprises four weft yarns.
 40. The fabric as recited in claim 30,wherein said fabric has at least two layers of fabric in certaindiscrete areas of the fabric and at least one single fabric layer at adiscrete area within said fabric, wherein the weave diagram for such afabric does not exhibit more than three consecutive filled or unfilledblocks in any row or column.
 41. The fabric as recited in claim 30,wherein said fabric has at least two layers of fabric in certaindiscrete areas of the fabric and at least one single fabric layer at adiscrete area within said fabric, wherein only two separate weavedensities are present within the fabric structure in the area of thejunction of the two layers and single fabric layer.
 42. An airbagstructure that does not exhibit significant change in pressurecharacteristic when collided with a broken glass surface at its peakpressure.
 43. A puncture resistant airbag comprising differentconstructions or coatings on the side facing the occupant and on theside facing outside, where the side facing the occupant has an ASTM F1342 puncture resistance of less than about 12 lbs. and the side facingthe outside of the vehicle has an ASTM F 1342 puncture resistance ofgreater than about 10 lbs.
 44. In an airbag cushion, the improvementcomprising: at least one exterior surface having an inner fabric layer,an intermediate coating, primer or adhesive layer, and an outer film orfabric layer, and having an ASTM D 4833 index puncture resistancegreater than about 210 lbs. and ASTM F 1342 puncture resistance greaterthan about 10 lbs.
 45. The airbag of claim 44, wherein said outer filmor fabric layer is a polyurethane film, and said coating, primer oradhesive layer is a polyurethane coating.
 46. The airbag of claim 45,wherein said film is about 3 mils thick and said coating is about 1.2ounces per square yard.
 47. The airbag of claim 44, wherein said airbagis at least one of puncture resistant and abrasion resistant.
 48. Theairbag of claim 44, wherein said at least one surface having an ASTM F1342 puncture force of at least about 10 lbs.
 49. The airbag of claim45, having a puncture force of at least about 25 lbs.
 50. The airbag ofclaim 41, wherein said at least one surface having an ASTM D 4833 indexof at least about 250 lbs.
 51. The airbag of claim 47, having an indexof at least about 300 lbs.
 52. An airbag cushion adapted for use betweenan occupant and a window comprising: an inner or inside surface, wall,construction, or coating adjacent the occupant, and an outer or outsidesurface, wall, construction, or coating adjacent the window, whereinsaid inner or inside surface, wall, construction, or coating adjacentthe occupant is at least one of lighter, softer, more flexible, and lessabrasive than said outer or outside surface, wall, construction, orcoating adjacent the window of said vehicle.